Picture transmission amplifier



Sept. 18, 1934. R, H N R 1,973,725

PICTURE TRANSMISSION AMPLIFIER Filed April 13, 1926 2 Sheets-Sheet l 12a 14a II l 13? A 136 INVENTOR P''% RICHARD H. RANGER TORNEY Sept. 18, 1934. R RANGER I 1,973,725

PICTURE TRANSMISSION AMPLIFIER Filed April 13. 1926 2 Sheets-Sheet 2 INVENTOR RICHARD H. RANGER TORNEY Patented Sept. 18, 1934 PATENT OFFICE 1,973,725 morons TRANSMISSION murmrma Richard H. Ranger, Newark, N. J., Radio Corporation of America, a

01' Delaware assignor to corporation Application April 13, 1926, Serial No. 101,612

Claims. (Cl. 178-7) My invention relates to picture transmission systems, and particularly to amplification systems for use in connection therewith.

An object of my invention is to provide an amplifier system in conjunction with a picture transmitting system adapted to cause the production of sharper detail in the picture as received over the signaling channel.

Another object of my invention is to provide an amplifier system in cooperation with a photo electric cell and an illumination effect integrating system, whereby the eiIect of the integrating system is modified in response to sudden changes in illumination of the photo-cell.

15 Another object of my invention is to provide an amplifier means adapted to produce a difierent amount of amplification of rapid electrical changes than it produces with slow electrical changes.

In the development of my photo modulator sysems, disclosed in my applications Serials Nos.

695,175 filed Feb. 26, 1924, now Patent No.

1,848,839, granted March 8, 1932, and 726,235

filed July 16, 1924., now Patent No. 1,790,722,

granted 'Feb. 5, 1931, I have produced systems for analyzing the lights and shades of a' picture into integrated current pulses which occur at a frequency and extend for a duration which are determined by the unit light intensity of the picture. The system as disclosed in the above mentioned copending applications contains a photo electric cell, amplifiers associated therewith and integrating, amplifying, and relaying means, combined with synchronized scan- M ning means, and reproducing means.

It has been found in the operation of the system as disclosed in the above mentioned application, that the total light from the picture being transmitted is efiectively and very accu- 40 rately integrated, but that no sudden responses are obtainable from the system in response to sudden changes in the light intensity from the print as the scanning means pass over its surface. In consequence there occurs a certain amount of loss of sharpness of outline and of detail.

My invention provides means whereby a sudden change in light from the picture causes an immediate response, with much less integration than the amount which occurs in the production of a uniform tint. This immediate response causes the production of much sharper lines in the reproduced picture, and much better detail. My invention provides this feature by means of modifications in the amplifying system which cause it to produce a much greater amplification of a rapid current change than is produced for a slow current change. By this means a sudden change in the light intensity from the print produces a very large output of amplified current, and therefore, causes actuation of the recording means almost independently of the integrating feature of the system. By this means much sharper outlines are obtained in the reproduced print, and therefore, much greater detail.

Other objects and structural details of my invention will be apparent from the following description when read in connection with the accompanying drawings, wherein:

Figure 1 shows a form of embodiment of my invention in combination with a photo-cell.

Figure 2 shows a preferred form of embodiment.

Figure 3 shows my device incorporated in the picture transmission system of the previously mentioned applications.

Figure 4 shows a print produced by the apparatus of my invention showing the extent to which the effect can be carried and,

Figure 5 is a specimen of a normal print as 30 produced by my system.

Referring to the figures a photo-electric cell 1 is provided, having a current supply source 2 and an output resistance 3.v A vacuum tube amplifier 4 is provided and connected thereto through a C battery 5. Filament heating means (not shown) are provided. In the anode circuit of the triode amplifier 4 are connected two output re sistances 6 and 7. The resistance 6 is shunted by a condenser 8 and the resistance 7 is connected to suitable anode current supply sources. The output from the vacuum tube amplifier 4 is taken from the resistance 7 and conveyed through a C battery 9 to an additional amplifier 10, the output from which in the anode circuit thereof may be utilized in any desired manner.

In the operation of this embodiment of my invention the resistances 3 and 7 serve as the coupling resistances of the usual resistance coupled amplifiers and function in the usual way, causing the transfer of amplified currents corresponding to the currents flowing in the photo electric cell 1. However, the full amplifying power of the triode 4 is not utilized under static conditions 105 because of the fact that a portion of the voltage ing potential drop in the output circuit of the no triode 4 is utilized. If, however, the light upon 1 the cell 1 changes suddenly a sudden change ocmitted as a pulse through the condenser8 and in consequence resistance 6 is, in effect, bypassed, with the result'that the full amplifier voltage drop occurs momentarily in the resistance '7, giv ing a much increased pulse of amplified current from the triode 10. This may be proportionately utilized. By this means rapidly changing currents are much more highly amplified than slowly changing currents.

Referring to Figure 2, showing a preferred embodiment of my invention, a photo electric cell 1 is provided as before and connected to a battery 2 and output resistance 3. An. amplifying triode 4 has its input circuit connected across resistance 3, and a similar triode amplifier 10 has its input circuit fed from the output energy of tube 4. These are, however, differently connected. An output resistance 7 is provided as before, and a bypass condenser 11 is connected between the anode circuit of the triode 4 and the grid circuit of the triode 10. shunting the condenser 11, is

provided, in series, a resistance 12, a C battery,

rent in the triode 4, the effect of which is conveyed directly and without loss through the condenser 11 to the gridof the triode 10, and full amplification thereof is thus obtained.

Referring to Figure 3, the preferred form of my invention is shown as embodied in Figure 1 of the previously mentioned application Serial No. 726,235.

The complete operation of the system disclosed therein with the preferred form of my present invention embodied therewith, will be readily understood by an examination of that application and the following outline.

As disclosed in that application the changes in light upon the photo cell 1 of Figure 3 affect the amplifiers 6 and '1 shown therein. The slow current changes are supplied to the amplifying triodes 14 and 15 which in turn cause the charging of the condensers 16 and 17 at a proportionate rate and cause the appropriate throw of the relays 22 and 29 in the fashion there disclosed. The devices of my present invention as embodied in the condensers 11a and 11b and the resistances 12a, 14a, 12b and 14b.

The result of the operation of my present invention when embodied in light photo transmission system is shown in Figures 4 and 5. In these examples Figure 4 shows the extent to which the process can be carried in the production of heavy tone values outlining the major details. It may be made to produce an effect which is almost one of hallation. It thus accentuates the major outlines predominantly.

When carried to a less extent it produces an efiect shown in Figure 5 which is that of a very great increase in detail and much improved sharpness of outline of the details.

It is to be noted that Figures 4 and 5 have been reproduced in the drawings by photo-mechanical processes since it has been found impossible to produce pictures of this character by manual means.

By. this means I am enabled to obtain prompt response of the relays 22 and 29 of my photo modulator system to sudden changes in light intensity on the photo cell 1 and integrated response to slow changes of light intensity.

While I have shown but one embodiment of my invention in the foregoing drawings and descriptions, it is capable of various modifications therefrom without departing from the spirit thereof, and it is desired therefore that only such limitations shall be imposed thereon as are required by the prior art 01 indicated by the claims.

I claim as my invention:

1. A method of reproducing pictures and the like which comprises translating light intensities corresponding to elemental areas of the picture to be reproduced into proportional electric current variations, controlling the number, time and intensity of such variations per unit of time in accordance with the light intensity of successive elemental areas of the picture, causing rapidly changing intensities of light on successive elemental areas of the picture to produce accentuated picture outlines, and suitably recording the picture from such variations in electric current.

2. In apparatus for translating variable light intensities into electric impulses, the combination of means for producing periodic impulses-normally of substantially equal duration and separated by periods of substantially equal duration, theduration of the impulses normally being equal to the duration of the separating periods, means for varying the duration of either of said periods, and means for initiating or terminating a marking period in accordancewith sudden changes of light intensities.

3. In apparatus for translating variable light intensities into electric impulses, the combination of means for producing periodic impulses nor-.

mally of substantially equal duration and separated by periods of substantially equal duration, and the duration of the impulses normally being equal to the duration of the separating periods, and means for varying the duration of either of said periods independently of the other, and means for initiating or terminating a marking period in accordance with sudden changes of light intensities. v

4. In apparatus for translating variable light intensity into variations of electric current, the combination of means for producing periodic impulses normally equal in length and separated by spacing periods normally equal in length, the time duration of the impulses normally having a predetermined ratio to the time duration of the separating periods for a predetermined intensity of light and means for increasing the said ratio for values of light intensity on one side of said predetermined value and for decreasing said ratio for values of light on the other side of said predetermined value of light intensity, and cooperating means for initiating or terminating a marking period in response to sudden variations in light intensity.

5. In modulating apparatus, the combination of a plurality of means for storing predetermined quantities of electricity, means for supplying electricity to said plurality of means at a predetermined normal rate, and means controlled by light appended intensity for varying the rate of supply of electricity to one of said storing means independently, and means actuated by sudden light intensity changes for further varying the rate of supply of electricity.

6. In apparatus for translating variations oi light intensity into variations of electric current, the combination of a pair of means for storing electricity, means for supplying electricity to said storing means at a predetermined normal rate and means controlled by light intensity for varying the rate of supply of electricity to one of said storing means in accordance with light intensity for variations of light intensity on one side of a predetermined value of light intensity and for varying the rate of supply of electricity to the other of said storing means in accordance with variations in intensity of light lying on the other side of said predetermined light intensity, and means cooperating therewith for further modifying the rate of supply of electricity to either thereof in accordance with sudden changes of light intensity.

'7. In an electro-optical image producing system having light translating elements and current amplifiers associated therewith, the method of accentuating variations in picture values which comprises converting varying intensity of light and shadow on elemental areas of a record, an image of which is to be transmitted, into proportional strength electric current impulses for amplification, and controlling the output circuit of the current amplifier so as to increase the output energy from the amplifiers at time intervals during a sudden change in picture light value over the average output energy produced by a slow change in the picture light value.

8. An amplifier system comprising a plurality of thermionic amplifiers for amplifying picture current impulses, and resistance and capacity elements connected directly in the output circuit of at least one of said amplifiers for varying the output energy from the amplifiers in accordance with the rate of change of current applied thereto.

9. The combination of an electric valve provided with input and output circuits, means including a device possessing capacitance arranged to apply a variable voltage to said input circuit, and impedance means directly connected in said output circuit for neutralizing the effect of variation in the frequency of said input voltage on the current of said output circuit.

10. The combination of an electric valve provided with input and output circuits, means including a photo-electric cell arranged to apply a variable voltage to said input circuit, and alternating current controlling means having a relatively high impedance with respect to said output circuit connected directly in said output circuit for neutralizing the capacitative effect of said cell on the current of said output circuit.

11. The combination of an electric valve provided with input and output circuits, input voltage control means including an input resistor and a device possessing capacitance connected in parallel with said resistor, and impedance means directly connected in said output circuit for new tralizing the capacitative effect of change in the frequency of said input voltage on the current of said output circuit, said impedance means having a relatively high impedance value with respect to the impedance of the output circuit.

12. I- combination, an electric valve having an input circuit and an output circuit, relatively high distributed capacity control means directly connected in said input circuit and compensating means connected in said output circuit for neutralizing the efiect of said capacity upon lead current flow in said output circuit, said compensating means comprising a current control resistor and a current control capacitor connected shunt with said current control resistor.

13. The combination of an electric valve pro= vided with input and output circuits, means including a device possessing capacitance arranged to apply a variable voltage to said input circuit, and impedance means directly connected in said output circuit for controlling the capacitative ef fect of variation in the frequency of said input voltage on the current of said output circuit.

14. The combination of an electric valve pro-= vided with input and output circuits, means in= eluding a photoelectric cell arranged to apply a variable voltage to said input circuit, and alternating'current controlling means having a relative high impedance with respect to said output circuit connected in said output circuit for controlling the capacitative effect of said cell on the current of said output circuit.

15. In combination, an electric valve having an input circuit and an output circuit, relatively high distributed capacity control means connected in said input circuit and compensating means connected in said output circuit for controlling the effect of said capacity upon load current flow in said output circuit, said compensating means comprising a current control resistor and a current control capacitor connected in shunt with said current control resistor. 

